1. Field of the Invention
The invention relates to a rotational speed sensor, a method for manufacturing a rotational speed sensor and to the use of the rotational speed sensor in motor vehicles.
2. Description of the Related Art
Rotational speed sensors are generally used to sense the angular speed of a system about a defined axis. An important field of application of rotational speed sensors is automobile engineering, for example in vehicle movement dynamics control systems such as the electronic stability program (ESP) or what is referred to as a rollover detection means. Such fields of application which are critical in terms of safety make particular requirements of rotational speed sensors in this context.
Document U.S. Pat. No. 6,230,563 B1 describes a Z axis rotational speed sensor which can therefore sense a rotational speed about its Z axis, the base area of its substrate being oriented parallel to the x-y plane (Cartesian coordinate system). This rotational speed sensor has two seismic masses which are coupled to one another by means of a coupling bar, wherein the coupling bar is suspended from the substrate by means of a torsion spring. The seismic masses are suspended directly from the substrate, with this suspension being embodied in such a way that it has to ensure the possibility of deflection of the seismic masses both for the drive and reading modes of the rotational speed sensor, as a result of which undesired crosstalk can occur between the two oscillation modes, which can have an adverse effect on the measurement.
Document WO 2006/034706 A1 proposes suspending the seismic masses from a frame which is itself suspended on the substrate. As a result, degrees of freedom of the suspension can be restricted in that, for example, the frame structure together with the seismic masses oscillates in the drive mode but in the reading mode only the seismic masses oscillate, as a result of which crosstalk between the two oscillation modes can be largely avoided. However, the coupling of the seismic masses by means of the proposed coupling unit is sensitive to parallel interference excitations in the measuring direction, such as, for example, shocks.